Pattern visualizer

Reverse Integer

The key insight: any integer can be reversed digit by digit using modular arithmetic (x % 10 extracts the last digit) and integer division (Math.floor(x / 10) drops the last digit), building the reversed number by shifting existing digits left (result * 10) and adding the new digit. This avoids string conversion entirely and processes the number in a single left-to-right pass through its digits. Animated on: Given a signed 32-bit integer x, reverse its digits and return the reversed integer..

Math

time O(n)space O(1)step 1 / 10

123

[0]

line 2

reversed = 0. Seed the reversed accumulator; no digits have been processed yet.

Pseudocode

1FUNCTION reverseInteger(x):
2  reversed = 0
3  WHILE x > 0:
4    digit = last digit of x (x mod 10)
5    reversed = reversed * 10 + digit
6    drop the last digit of x (integer divide x by 10)
7  RETURN reversed

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